Airline delays and cancellations have dropped significantly in the past few years. That’s what
federal statistics show, but the numbers might not be telling the whole story.

That is one of the conclusions in a report by the office of inspector general for the U.S.
Department of Transportation, which recommends new ways of calculating airline delays.

The department’s data says that airline delays fell by 33 percent from 2000 to 2012, while
flight cancellations dropped by 56 percent at the nation’s largest airports.

The problem with the numbers, the inspector general says, is that the department looks at flight
data from only the 16 largest airlines. Those airlines account for about 76 percent of domestic
flights. The other 24 percent are not calculated in the federal analysis.

The nation’s “published flight delay data present the public with an incomplete picture of the
number of delays that actually occur at a given airport or are generated by all carriers,” the
report said.

Another reason the numbers don’t give an exact picture, the report says, is that most major
airlines have increased their scheduled gate-to-gate time for nearly every flight, giving
themselves a cushion to absorb delays.

In 2000, the time that airlines scheduled for a flight exceeded the actual flight time on 73
percent of routes analyzed by the office of inspector general. By 2012, this had grown to 98
percent of all routes. One example cited by the study was a New York LaGuardia-to-Indianapolis
route — typically a 2 1/2-hour flight. From 2000 to 2012, airlines have increased the scheduled
flight time by 21 minutes, the report found.

Airlines say that they don’t inflate the scheduled flight time to avoid delays but try to be
realistic about the time each flight needs.

“Airline scheduling is based on the realities of the air travel system, taking into account
conditions such as airspace and ground congestion or weather that can impact gate-to-gate time,”
said Vaughn Jennings, a spokesman for Airlines for America, the trade group for the nation’s
airlines.